Abstract The piles of channel bridges generally exist in the form of steel casing composite piles (SCC pile, namely, the reinforced concrete pile wrapped by steel casing) owing to construction factors, such as drilling and temporary platforms. To investigate the effect of steel casings on the behaviors of the original reinforced concrete (RC) piles, and to clarify the reasons for this effect, we conducted a lateral loading experiment on three sets of piles. The three sets of piles included a set of RC piles, a set of SCC piles with partially set steel casings, and a set of piles with fully set steel casings. Each set comprised two identical specimens. In addition, to provide a theoretical basis for determining appropriate parameters for steel casings in practice, parameter analysis was conducted by numerical modeling. The results indicated that the contact force between the steel casing and the RC shaft directly caused the transformation of failure mode of the pile. When the length of steel casing was insufficient, the accumulated contact force resulted in great shear force and bending moment in the uncased RC shaft, and the failure mode of the pile would transform from bending to bending-shear failure. The mechanical behaviors and failure modes of SCC piles were significantly affected by the relative position between the steel casing and the equivalent plastic zone of the original RC shaft. Only if the equivalent plastic zone of the original RC shaft was wrapped by the steel casing, the critical state would be governed by the steel casing, and the bearing capacity and toughness of SCC pile would be significantly improved. Moreover, a fitting formula of the optimum length-to-diameter ratio for a steel casing was proposed, and the most unfavorable length-to-diameter ratio was discussed.

中文翻译：

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侧向荷载作用下钢套管复合桩性能及参数优化

摘要 渠道桥桩由于钻井、临时平台等施工因素，一般以钢套管复合桩（SCC桩，即钢套管包裹的钢筋混凝土桩）的形式存在。为了研究钢套管对原钢筋混凝土 (RC) 桩行为的影响，并阐明这种影响的原因，我们对三组桩进行了侧向加载试验。三组桩包括一组RC桩、一组部分下沉钢套管的SCC桩和一组完全下沉钢套管的桩。每组包括两个相同的样本。此外，为在实践中确定合适的钢套管参数提供理论依据，通过数值模拟进行参数分析。结果表明，钢套管与钢筋混凝土轴的接触力直接引起了桩身破坏模式的转变。当钢套管长度不足时，累积接触力导致无套管钢筋混凝土轴产生较大的剪力和弯矩，桩的破坏模式将由弯曲破坏转变为弯剪破坏。SCC桩的力学行为和破坏模式受钢套管与原钢筋混凝土轴等效塑性区的相对位置的显着影响。只有将原钢筋混凝土轴的等效塑性区用钢套管包裹，才能使钢套管控制临界状态，才能显着提高SCC桩的承载力和韧性。而且，